Multilayer composite films and articles prepared therefrom

ABSTRACT

The present invention is an optically transparent laminate film comprising: at least three layers of film, wherein at least two of the at least three layers comprise ionomeric films, and wherein the film can be suitable for use in a photovoltaic cell or in packaging.

This application claims the priority from U.S. Application No.60/634,421, filed Dec. 7, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to laminate films useful in packaging in generaland as encapsulants in photovoltaic modules in particular. The inventionparticularly relates to transparent packaging films comprising ethyleneacid copolymer ionomers.

2. Description of the Related Art

Good optical properties are important in packaging materials in generaland solar cell modules in particular because good performance requiresthat light incident to the cell be transmitted efficiently andeffectively to the voltage-generating layer. Poor light transmissionreduces the efficiency and/or productivity of the photovoltaicgeneration process.

For example, a common form of solar cell module is made byinterconnecting individually formed and separate solar cells made forexample of crystalline silicon, and then mechanically supporting andprotecting the cells against environmental degradation by integratingthe cells into a laminated solar cell module. The laminated modulesusually comprise a stiff transparent protective front panel or sheet,and a rear panel or sheet typically called a “backskin”. Disposedbetween the front and back sheets so as to form a sandwich arrangementare the interconnected solar cells and an encapsulant.

A necessary requirement of the encapsulant (or at least that portionthereof that extends between the front sides of the cells and thetransparent front panel) is that it be transparent to solar radiation.The typical mode of forming the laminated module is to assemble asandwich comprising in order: a transparent panel, e.g., a front panelmade of glass or a transparent polymer, a front layer of at least onesheet of encapsulant, an array of solar cells interconnected byelectrical conductors (with the front sides of the cells facing thetransparent panel), a back layer of at least one sheet of encapsulant,and a backskin or back panel, and then bonding those components togetherunder heat and pressure using a vacuum-type laminator. The back layer ofencapsulant may be transparent or any other color, and prior art moduleshave been formed using a backskin consisting of a thermoplastic orthermosetting polymer, glass or some other material.

A further requirement of the encapsulant is dimensional stability. Inorder to avoid potentially damaging stresses on the silicon cell, theencapsulant and surrounding structure should be stable to thetemperature fluctuations that are found in end-use locations of themodule.

A large number of materials have been used or considered for use as theencapsulant in modules made up of individual silicon solar cells.Ethylene vinyl acetate copolymer (commonly known as “EVA”) is commonlyused as an encapsulant for modules comprising crystalline silicon solarcells. However, EVA may have certain limitations or deficiencies, suchas its tendency to discolor. Also, it can decompose and release aceticacid. EVA also can require cross-linking—for example as described inU.S. Pat. No. 6,093,757—to impart dimensional stability. Cross-linkingis a potential source of variability in the product, and can promotesubsequent oxidation and degradation of EVA. In addition, EVA must belaminated in a vacuum when making a module because of the presence ofperoxide as a cross-linking promoter in the EVA. EVA used as anencapsulant material usually contains 33% (by weight) of vinyl acetate,and thus is a very soft and tacky material that makes handling EVA in amanufacturing environment somewhat troublesome.

The use of ionomer as an encapsulant is described in U.S. Pat. No.5,478,402, hereby incorporated herein in its entirety by reference. Theuse of ionomer as an encapsulant is further disclosed in U.S. Pat. No.5,741,370. The term “ionomer” and the type of resins identified therebyare well known in the art, as evidenced by Richard W. Rees, “IonicBonding In Thermoplastic Resins”, DuPont Innovation, 1971, 2(2), pp.1-4, and Richard W. Rees, “Physical Properties And Structural FeaturesOf Surlyn® Ionomer Resins”, Polyelectrolytes, 1976, C, 177-197. Ionomersmay be formed by partial neutralization of ethylene-methacrylic acidcopolymers or ethylene-acrylic acid copolymers with organic bases havingcations of elements from Groups I, II, or III of the Periodic Table,notably, sodium, zinc, aluminum, lithium, magnesium and barium. Surlyn®ionomers have been identified as copolymers of ethylene and methacrylicor acrylic acid that typically have a melting point in the range of83-95° C.

It can be desirable to provide materials that are useful as encapsulantmaterials in photovoltaic cells, wherein cross-linking is not requiredfor acceptable dimensional stability of the encapsulant material.

SUMMARY OF THE INVENTION

The present inventors have made the surprising discovery that one ormore physical properties of a polymer can be significantly improved whenthe polymer is sandwiched as a core layer in a laminate between ionomerlayers.

In one aspect, the present invention is a laminate comprising: at leastthree polymeric layers which include

(1) two outer polymeric layers that are ionomeric polymers, and(2) at least one core layer unit;wherein each of the outer layers is in direct contact with opposingsurfaces of at least one surface of a core layer unit, and wherein theat least one core layer unit is a single or multiple layer polymericfilm or sheet that comprises at least one non-ionomeric polymer layerand wherein the optical clarity, as measured by the transmittance, andthe dimensional stability of the laminate are each respectively enhancedover the expected values of said properties for the individual laminatelayers.

In another aspect, the present invention is a laminate comprising:

(i) a first outer layer comprising a first ionomer;(ii) a core layer unit comprising at least one polymer layer positionedsuch that a first surface of the core layer unit is in direct contactwith at least one surface of the first outer layer;(iii) a second outer layer comprising a second ionomer positioned suchthat a second surface of the core layer unit is in direct contact withat least one surface of the second outer layer;wherein the at least one core layer polymer is a non-ionomeric polymerand wherein the individual optical transmittance for each of the firstionomer layer, the second ionomer layer, the core layer unit, and thelaminate at the same wavelength can each be measured, and wherein themeasured transmittance for the laminate is greater than the expectationvalue of the transmittance calculated from the transmittance of thethree individual layers in their non laminated state weighted by theirthicknesses in the laminate.

In another aspect, the present invention is a solar cell modulecomprising an encapsulant comprising:

(i) a first outer layer comprising a first ionomer;(ii) a core layer unit comprising at least one polymer layer positionedsuch that a first surface of the core layer unit is in direct contactwith at least one surface of the first outer layer;(iii) a second outer layer comprising a second ionomer positioned suchthat a second surface of the core layer unit is in direct contact withat least one surface of the second outer layer;wherein the at least one core layer polymer is a non-ionomeric polymerand wherein the individual optical transmittance for each of the firstionomer layer, the second ionomer layer, the core layer unit, and thelaminate at the same wavelength can each be measured, and wherein themeasured transmittance for the laminate is greater than the expectationvalue of the transmittance calculated from the transmittance of thethree individual layers in their non laminated state weighted by theirthicknesses in the laminate.

In another aspect, the present invention is a plurality ofinterconnected solar cells comprising an encapsulant comprising;

(i) a first outer layer comprising a first ionomer;(ii) a core layer unit comprising at least one polymer layer positionedsuch that a first surface of the core layer unit is in direct contactwith at least one surface of the first outer layer;(iii) a second outer layer comprising a second ionomer positioned suchthat a second surface of the core layer unit is in direct contact withat least one surface of the second outer layer;

wherein the at least one core layer polymer is a non-ionomeric polymerand wherein the individual optical transmittance for each of the firstionomer layer, the second ionomer layer, the core layer unit, and thelaminate at the same wavelength can each be measured, and wherein themeasured transmittance for the laminate is greater than the expectationvalue of the transmittance calculated from the transmittance of thethree individual layers in their non laminated state weighted by theirthicknesses in the laminate.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the present invention is a laminate article having(a) outer layers that comprise ionomeric polymers and (b) a core layerunit that is disposed between the outer layers and comprises a nonionomeric polymer. In a laminate of the present invention the measuredoptical and/or dimensional stability of the laminate can be enhancedover the expected value of either or both said properties for theindividual layers of the laminate.

By “expectation value” of a property it is meant the predicted value ofsaid laminate property as calculated from the individual layers of thelaminate, taking into account the layer thickness weighted average. Byway of illustration, a three layer laminate wherein each layer has anoptical extinction coefficient would be expected to have an absorbancethat is the layer thickness weighted sum of the individual extinctioncoefficients. Similarly a three layer laminate where each layer has atensile modulus would be expected to have a tensile modulus that is alayer thickness weighted average of the individual layers.

A laminate, as the term is used herein, comprises multiple polymerlayers in face to face relationship among each other, wherein theadhesion between the layers is such that the layers remain adheredtogether during the application of such stresses as the structure issubjected to during normal or intended use of said laminate. Adhesioncan be accomplished by the use of polymers in the different layers thatadhere to each other during the manufacture of the material, or by theuse of additional adhesives or primers.

The outer layers of the present invention are structural layers of alaminate of the present invention that are positioned so that they arein direct contact with a core layer unit on at least one surface of saidcore layer unit. The outer layers of a laminate of the present inventioncontribute to good optical properties in a laminate of the presentinvention. The outer layers of a laminate of the present inventioncomprise ionomeric polymers (ionomers). The outer layers each cancomprise the identical ionomer composition to one another or can bedifferent ionomer compositions from one another. Ionomers useful in thepractice of the present invention are copolymers obtained by thecopolymerization of ethylene and an ethylenically unsaturated C₃-C₈carboxylic acid. Preferably the unsaturated carboxylic acid is eitheracrylic acid or methacrylic acid. The acid copolymer preferably includesfrom about 8 wt % to about 25 wt % of the acid, based on the totalweight of the copolymer. Ionomers useful as optical layers in thepractice of the present invention preferably comprise from about 11 wt %to about 25 wt % acid, more preferably from about 14 wt % to about 19 wt% acid, and most preferably from about 15 wt % to about 19 wt % acid.

Ionomers suitable for use herein can include a third comonomer componentwhich is an ester of an ethylenically unsaturated C₃-C₈ carboxylic acid.The alkyl substituent of the ester can preferably be derived from a C₁to C₁₂ alcohol, but any unsaturated ester that can provide the opticalproperties described herein can be suitable for use in the practice ofthe present invention. Conventional ionomers that include a thirdcomonomer are commercially available from E.I. du Pont de Nemours andCompany, for example, and can be suitable for use in the practice of thepresent invention so long as the optical and physical properties aresuitable for application in the present invention.

A core layer unit of the present invention is a structural componentwithin a laminate of the present invention that is in direct contactwith at least one outer layer on at least one surface of the at leastone outer layer. The core layer unit of the present invention providesproperties to the laminate that are not provided by the outer layersalone. For example, the core layer can provide higher or lower modulus,barrier properties, strength, absorbancy, permeability, or otherproperties desirable in a package or other article.

The core layer unit can itself be a single polymeric layer, or alaminated polymeric structure, or multiple plied layers of film and/orsheet. Any layer included or used in a core layer unit of the presentinvention is, for the purposes herein, considered a core layer. A corelayer suitable for use herein can comprise any polymer that impartsdesirable properties to the laminate. For example, the core layer can bepolyurethane, ethylene vinyl acetate (EVA), polyvinyl chloride (PVC),polyester, polyacetals, ethylene acid copolymers (which can be inclusiveof ethylene acid terpolymers or higher copolymers), ethylene acrylatecopolymers (which can be inclusive of terpolymers and highercopolymers), or other polymeric layers that have suitable physicalproperties and can be laminated to an ionomer to yield a multilayer filmeither directly or through a tie or adhesive layer. A laminate of thepresent invention can comprise more than one core layer unit.

In another embodiment, the present invention is an optically transparentmultilayer laminate film structure comprising at least three filmlayers. By optically transparent it is meant that optical measurementstaken on the combination of the at least three layers of the multilayerfilm structure are at least 85% transparent to light in the visibleregion of the light spectrum. Optical transparency can be related to thehaze of the multilayer laminate film. In the practice of the presentinvention, the haze of the multilayer laminate structure is not greaterthan 6%.

A optically transparent laminate of the present invention is constructedsuch that the outer layers contact the core layer and form an interfacewith opposing surfaces of the at least one core layer.

While the laminate structure of the present invention transmits at leastabout 85% of the incident light, and/or has a haze of less than about6%, the individual components of the laminate are not required to haveoptical properties that meet those standards. In particular, the atleast one core layer of the present invention is not required to haveoptical properties which meet the minimum optical standards of thelaminate. In fact, it is one object of the present invention to overcomerelatively poor optical properties in a core layer component bycombining core structural layer(s) with outer layers, or optical layers,of the present invention described herein, thereby providing a laminatehaving acceptable optical properties.

In another embodiment, an optically transparent multilayer laminate ofthe present invention comprises: (1) at least two ionomeric outer layershaving independently transparency of at least about 85% and/or a hazevalue of less than about 6%, and (2) at least one core layer thatprovides other desirable properties not provided by the optical layersbut having a transparency of less than about 85% and/or a haze ofgreater than about 6% when taken alone and not in a laminate with theouter layers.

The outer layers can each independently transmit at least about 85% ofincident light. Preferably the outer layers transmit at least about 88%of incident light, and more preferably at least about 89% of theincident light. Most preferably the outer layers transmit at least about90% of incident light. In a much preferred embodiment the outer layerscan each independently transmit at least about 91%, 92%, 93%, 94%, 95%or more of incident light. The haze of the outer layers is preferablyless than about 5%, more preferably less than about 4%, and mostpreferably less than about 3%. In a particularly preferred embodiment ofthe present invention, the haze of the outer layers is less than about2%, and can be as low as 1% or less, and light transmission can be atleast 98% or even 99% or more.

In the practice of the present invention the outer layers of themultilayer film are chemically distinct from the at least one core layerand can be chemically distinct from each other. To illustrate by way ofexample, the percentage of the acid component in the ionomer can varybetween the at least two of the ionomer layers, as can the level ofneutralization of the acid components, as can the identity of thecounterion present in the at least two ionomers, as can the presence orabsence of a third comonomer. Each of these conditions, and others, canbe varied independently or in combination to make the outer layerschemically distinct from the core layer and/or from each other. It canbe preferable, for reasons of cost or to reduce complexity, that theouter layers are identical to each other.

In a preferred embodiment of the present invention a laminate of thepresent invention has a transition temperature as measured by DMA (anddescribed hereunder in the examples) of 65° C. or more at 1 Hz. Morepreferably, the transition temperature of the material is greater thanabout 65° C. and that of the core layer alone is 40° C. or less at 1 Hz.

A transparent multilayer film of the present invention can be suitablefor use as an interlayer in a laminate glazing system such as: a vehiclewindshield or sidelite; as safety glass in buildings; cabinet glass;glazing in doors; shelving; laminated glazing in other conventionalapplications.

A multilayer film of the present invention surprisingly exhibitssuperior optical properties compared to the core layer alone, and theouter layers provide other physical properties to the multilayer film.This result is surprising because the optical layers can providedesirable optical properties in spite of poor optical properties of thecore layer(s).

The multilayer laminate of the present invention has a total thickness40.0 mil or less. Preferably, the laminate can have a total thickness of20.0 or less. More preferably, the laminate can have a total thicknessof 10.0 mil or less, and even more preferably a thickness of 4.0 mil orless. Even more preferably, the laminate can have a total thickness ofabout 3.0 mil or less, or 2.0 mil or less. The thickness required of amultilayer film can be a balance between obtaining structural propertiesrequired to protect the contents of a package, for example, andachieving other goals such as meeting optical requirements oftransparency, using cost-effective materials, and/or minimizingproduction costs.

The outer layers of the present invention can be thinner than the corelayers of the present invention, but this may not be a requirement inall applications of the present invention. The thickness of the outerlayer(s) can each independently be about 50% or less of the thickness ofthe outer layer. The outer layers of a laminate of the present inventioncan each independently have a thickness of 20.0 mil or less, preferably15 mil or less, and more preferably 10 mil or less, with the provisothat any film thickness can be varied to balance the desirable opticaland other physical properties, with the practical aspects of producing acost-effective film.

A multilayer laminate film of the present invention can be useful in avariety of applications and can be suitable for use in combination withglass, or clear plastic, to make optically clear or transparent laminatearticles such as solar cell modules, or laminated windows, or othersafety glass, or plastic bottles, or squeezable bottles.

In another embodiment, the present invention is a photovoltaic cell inwhich a light sensitive silicon device is disposed against one of theionomer comprising layers of the multilayer laminate (“the first layer”)wherein the outer layers comprise ionomers and an inner, core, layercomprises a non ionomeric polymer. The light sensitive portion of thesilicon device faces the three layer laminate. The other surface of thesilicon device is disposed against a second layer that may comprise asecond three layer laminate, or any polymer that can form a seal againstthe first layer. The second layer may also comprise a backsheet layer,and the backsheet layer can be laminated with the second layer orseparate therefrom.

In a preferred embodiment the invention is a solar cell modulecomprising at least one solar cell which in turn comprises a transparentencapsulant material positioned adjacent to at least one surface of thesolar cell. The encapsulant material comprises a laminate materialfurther comprising:

(i) a first outer layer comprising a first ionomer;(ii) a core layer unit comprising at least one polymer layer positionedsuch that a first surface of the core layer unit is in direct contactwith at least one surface of the first outer layer;(iii) a second outer layer comprising a second ionomer positioned suchthat a second surface of the core layer unit is in direct contact withat least one surface of the second outer layer;wherein the at least one core layer polymer is a non-ionomeric polymerand wherein the individual optical transmittance for each of the firstionomer layer, the second ionomer layer, the core layer unit, and thelaminate at the same wavelength can each be measured, and wherein themeasured transmittance for the laminate is greater than the expectationvalue of the transmittance calculated from the transmittance of thethree individual layers in their non laminated state weighted by theirthicknesses in the laminate.

A module of the present invention further comprises a front supportlayer formed of light transmitting material disposed adjacent a frontsurface of the encapsulant material and a backskin layer disposedadjacent a rear surface of the encapsulant material.

The solar cell module can further comprise at least one solar cell thatin turn comprises a plurality of interconnected solar cells.

In another embodiment, the present invention is a laminate thatcomprises outer layers that in turn comprise ionomers, and a core layerthat is disposed between the outer layers and comprises a non ionomericpolymer such that the phase transition temperature of the laminate isenhanced over what would be expected from the individual laminate layersalone. It is possible for the laminated structure to have a DMA phasetransition temperature under dynamic mechanical analysis that is higherthan the phase transition temperature of the material from which thecore material is fabricated. The enhanced transition temperature yieldsa material which is dimensionally stable at ambient temperatures.Optionally the laminates of this embodiment have optical transparency,however this embodiment of the invention is not limited to transparentlaminates.

EXAMPLES

The Examples and Comparative Examples are presented for illustrativepurposes only, and are not intended to limit the scope of the presentinvention in any manner.

In the following experiments cast film was made on a Sano multi-layerextrusion line. The total structure of thickness 460 microns structurecomprised of 25 micron thick identical Surlyn® 1705-1 (Du Pont,Wilmington, Del.) outer layers bounding a 410 micron thick core layercomprising a second resin.

Secant Modulus was measured on film samples (Instru-Met load frame 1122tensile tester using ASTM D 882-01)°

% Haze was measured on film samples (BYK Gardner haze-gard plus usingASTM D 1003-00)°

% Transmittance was measured on film samples (Varian Cary 5 uv/vis/nir,System I.D. Cary5-1081139 scanned from 800 nm to 200 nm and reported at500 nm). The expectation value of the transmittance was calculated asthe layer thickness weighted value calculated from the absorbance perunit thickness of the materials that each layer comprised.

Dynamic mechanical analysis (DMA) was conducted in order to ascertainthe dimensional stability of the samples. The experiments were run on aSeiko DMS 210 in tensile mode from ambient to 150° C. at 1° C./minheating rate, 1 Hz frequency and 10 μm amplitude. By “DMA transition” ismeant the temperature at which the gradient of the length of thespecimen vs temperature plot sharply changes direction, indicatingeither shrinkage or expansion of the sample, that is a lack ofdimensional stability (dimensional instability), at the giventemperature.

In the following examples, Elvaloy® 1330 is ethylene-methyl acrylatecopolymer with 30% MA and 3 melt index (MI). Elvaloy® 1335 isethylene-methyl acrylate copolymer with 35% MA and 3 MI. Elvaloy® 3427is ethylene-butyl acrylate copolymer with 27% BA and 4 MI. Surlyn®1705-1 is a 5.5 MI, zinc-neutralized ethylene-methacrylic acid copolymerand Surlyn® 1857 is a 4 MI, zinc-neutralized ethylene-methacrylicacid-isobutyl acrylate terpolymer.

DMA Data Control Samples

Observed DMA Film Composition Transition (° C.) S1705 82 S1857 NM E133533 E1330 35 E3427 38 NM = Not Measured.

Laminate Samples

Film Composition Observed Transition S1705/E1330/S1705 78S1705/E1335/S1705 75 S1705/E3427/S1705 74

DMA data at 1 Hz from 0° C.-150° C. indicate that having a thin laminateof Surlyn® (1-mil) outside an EMA core (16-mil) provides dimensionalstability of the multi-layer structure at from ambient temperatures upto more than 70° C. with results almost equivalent to the mono-layerSurlyn® 1705-1 .

Optical and Tensile Data Control Samples

Observed Observed MD Transmittance Secant Modulus TD Modulus FilmComposition (%) (psi) (psi) S1705 90.5 29459 26930 S1857 89.4 NM NME1335 37.3 992 744 E1330 34.1 1727 1458 E3427 75.7 3310 3310

Laminate Samples

Expectation Observed Film Composition Transmittance (%) Transmittance(%) S1705/S1875/S1705 89.4 89.7 S1705/E1330/S1705 38.0 88.1S1705/E1335/S1705 41.2 85.1 S1705/E3427/S1705 77.2 88.1

Tensile Data (Secant Modulus)

Expected Observed Expected Observed MD MD TD TD modulus Modulus modulusModulus Film Composition (psi) (psi) (psi) (psi) S1705/E1330/S1705 48084733 4288 5071 S1705/E1335/S1705 4155 4320 3654 4846 S1705/E3427/S17056215 7498 5934 7729

The transparency of tri-layer structures is improved over monolayerElvaloy® AC films, however the advantages of the low modulus of the EMAis retained, while the dimensional stability as measured by the DMAtransition) of tri-layer structure is also significantly improved overmonolayer Elvaloy® AC films. The need for cross linking of the corelayer is obviated.

The present invention has been described with regard to certainembodiments and examples. However one skilled in the art will be ablewith obvious modifications to modify the invention. The scope of theinvention as claimed is intended to include all such modifications andis not to be construed to be limited to the examples and embodimentsdescribed herein.

1. A laminate article comprising: (i) a first outer layer comprising afirst ionomer; (ii) a core layer comprising at least one polymer layerand positioned such that a first surface of the core layer is in directcontact with at least one surface of the first outer layer; (iii) asecond outer layer comprising a second ionomer and positioned such thata second surface of the core layer is in direct contact with at leastone surface of the second outer layer; wherein the at least one corelayer polymer is a non-ionomeric polymer and wherein the individualoptical transmittance for each of the first ionomer layer, the secondionomer layer, the core layer unit, and the laminate at the samewavelength can each be measured, and wherein the measured transmittancefor the laminate is greater than the expectation value of thetransmittance calculated from the transmittance of the three individuallayers in their non-laminated state weighted by their thicknesses in thelaminate; or wherein the laminate article, the first ionomer and thesecond ionomer and the core layer polymer are characterized by atransition temperature measured under tensile conditions at 1 Hz by DMAsuch that the value of the transition temperature for the laminatearticle is greater than the value of the transition temperature of thecore layer polymer measured under identical conditions in anon-laminated state.
 2. The laminate article of claim 1 wherein thefirst outer layer and the second outer layer comprise identicalcompositions.
 3. The laminate article of claim 1 having an opticaltransmittance of light of 500 nm wavelength that is greater than 85%. 4.The laminate article of claim 1 which shows a DMA transition temperatureof greater than 65° C. at 1 Hz.
 5. The laminate article of claim 4wherein the core layer polymer shows a DMA transition temperature ofless than 40° C. at 1 Hz when not laminated to the outer layers.
 6. Thelaminate article of claim 1 wherein the core layer polymer is alaminate.
 7. The laminate article of claim 1 wherein the core layerpolymer comprises a polymer selected from the group consisting of:polyurethane; ethylene vinyl acetate (EVA); polyvinyl chloride (PVC);polyester; polyacetals; ethylene acid copolymers, ethylene acrylatecopolymers and blends, laminates or combinations thereof.
 8. Thelaminate article of claim 1 wherein the first ionomer and the secondionomer independently comprise a copolymer obtained by thecopolymerization of ethylene and an ethylenically unsaturated C₃-C₈carboxylic acid.
 9. The laminate article of claim 1 wherein the firstionomer and the second ionomer independently comprise an acid copolymerthat includes from about 8 wt % to about 25 wt % of the acid, based onthe total weight of the acid copolymer.
 10. The laminate article ofclaim 9 wherein the first ionomer and the second ionomer independentlycomprise an acid copolymer that includes from about 11 wt % to about 25wt % of the acid, based on the total weight of the acid copolymer. 11.The laminate article of claim 10 wherein the first ionomer and thesecond ionomer independently comprise an acid copolymer that includesfrom about 14 wt % to about 19 wt % of the acid, based on the totalweight of the acid copolymer.
 12. The laminate article of claim 11wherein the first and second ionomers independently comprise an acidcopolymer that includes from about 15 wt % to about 19 wt % of the acid,based on the total weight of the acid copolymer.
 13. An opticallytransparent laminate film comprising: at least three layers of film,wherein (a) at least two of the at least three layers of film comprisean ionomeric film (b) at least one of the at least three layers of filmindependently in a non-laminated state (i) transmits less than about 85%incident visible light or (ii) has a haze value of equal to or greaterthan about 6% as measured according to ASTM D1003-00 on the at least onelayer having a thickness of about 40 mil or less and (c) the transparentlaminate (i) transmits at least about 85% of incident visible light or(ii) has a haze value of equal to or less than about 6% as measuredaccording to ASTM D1003-00.
 14. An article comprising the opticallytransparent laminate film of claim
 13. 15. The article of claim 14wherein the article is a package or container.
 16. The article of claim15 wherein the article comprises one or more layers of glass laminatedto at least one of the ionomeric films. 17-29. (canceled)
 30. Thelaminate article of claim 1 wherein the first ionomer or the secondionomer independently comprises a copolymer obtained by thecopolymerization of ethylene; an ethylenically unsaturated C₃-C₈carboxylic acid; and an alkyl ester of a second ethylenicallyunsaturated C₃-C₈ carboxylic acid.
 31. The laminate article of claim 1that is produced by extrusion.
 32. The laminate article of claim 1,further comprising one or more layers of glass laminated to at least oneof the first outer layer or the second outer layer.
 33. A laminateglazing system comprising the laminate article of claim 32 and selectedfrom the group consisting of: a vehicle windshield or sidelite; alaminated window; other safety glass in buildings; cabinet glass;glazing in a door; shelving; other laminated glazing.